Moved promise flow into lib.
Added promise.errorListener().
Removed error listener.
Adding protos. Added proto/mixin.
Added tests for proto/mixin.
Added a test for proto/stack.
Temporally disabled promise flow - not ready.
Rebuilt mixable() with proto/mixin.
Merge pull request #38 from devo-ps/promiseFlow

Building things into proto.
Release 0.4.0
Sync with master